Disk storage accessing system

ABSTRACT

A disk storage accessing system that can disperse the load of each SAN disk storage accessed from a plurality of computers. An access frequency counter  124/134  counts a frequency of accesses to a disk storage of its computer. A resource monitoring/management unit  101  inquiries a resource monitoring unit  121/131  so that counted access frequencies of the disk storages are collected, totaled, then stored in a table  103.  When the totaled access frequency of the disk storage is over a first predetermined value, the system requests a SAN controller  102  to copy the disk volume; under a second predetermined value, requests the SAN controller to delete the disk volume. Then, the SAN controller instructs a DKU controller  111  so that: the DKU controller  111,  when being instructed to copy, instructs the copy source DKC to copy the disk volume into another disk storage; the DKU controller, when being instructed to delete, instructs the target DKC to delete the copied volume. The SAN controller  102,  after the copying/deletion ends, instructs a LU change controller  123/133  to change access paths so as to access the target disk storage.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to the accesses to SAN (StorageArea Network) disk storages, more specifically to an accessing systemfor disk storages that disperses the access load of each of those diskstorages.

[0003] 2. Description of Related Art

[0004] There is a well-known method in JP-A No. 99272/2000 for sharingdisk storages among a plurality of computers connected to those storagesvia a dedicated network such as fiber channel.

[0005] This technique is referred to as SAN, which assures the highfreedom in assignment of disk storages and computers so that a computercan be assigned to any of necessary disk storage areas flexibly.

[0006] In recent years, information handling systems that are accessedvia the Internet are considered increasingly to be important. Inparticular, many computer systems have come to be built as Web serversfor supplying various kinds of contents.

[0007] Such a Web server often includes an unspecific number of clientcomputers, and accordingly it is accessed so frequently that it isdifficult to estimate the peak time of accesses.

[0008] JP-A Nos. 271447/1998 and 69467/1998 disclose well-known methodsfor dispersing accesses to such a computer system so as to solve theabove problem.

[0009] The JP-A No. 271447/1998 discloses a technique for dividing fordispersing accesses in which each content is divided into small piecesso as to be stored in a plurality of disk storages.

[0010] In this case, the access load in proportion to the number of diskstorages can be dispersed, but the technique cannot cope with accessesover an estimated value.

[0011] The JP-A No. 69467/1998 also discloses a technique also fordispersing the access load with use of a plurality of server computers,but it is still difficult to disperse the load of each disk storage.

[0012] The SAN enables a plurality of computers to share a plurality ofdisk storages, but it cannot maintain its performance when the number ofcomputers increases excessively, since the load of each of the shareddisk storages increases.

SUMMARY OF THE INVENTION

[0013] Under the circumstances, it is an object of the present inventionto provide a method for dispersing the access load of each disk storage,which can correspond to changes of the load of a disk storage on whichaccesses are concentrated from a plurality of the computers in the SAN.

[0014] In order to achieve the above object, the disk storage accessingsystem of the present invention is provided with counting means forcounting the disk storage access frequency of each computer that refersto a disk storage; instructing means for collecting and totaling afrequency of each computer accesses to the disk storage, and instructingthe disk storage to copy its contents into one or more other diskstorages and instructing the computer that has accessed the copy sourcedisk storage after receiving a report on completion of the copying whenthe totaled access frequency is higher than a predetermined value so asto change the access paths and access a target disk storage from thecopy source disk storage; and means for changing access paths so as toaccess a target disk storage from the computer according to theinstruction.

[0015] When instructing a computer that accesses a copy source disk tochange access paths so as to access a target disk storage from thesource disk storage, the instruction is done to the computer that is thehighest in the access frequency to the source disk storage.

[0016] When data in the copy source disk storage is updated, the updateddata is copied into one or more of the target disk storages again.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is an overall block diagram of a disk access managementsystem of the present invention.

[0018]FIG. 2 is a flowchart of the processings executed by a resourcemonitoring/management unit of the present invention.

[0019]FIG. 3 is a flowchart of the processings executed by a SANcontroller of the present invention.

[0020]FIG. 4 is a flowchart of the processings executed by a DKUcontroller of the present invention.

[0021]FIG. 5 is a flowchart of the processings executed by a resourcemonitoring unit of the present invention.

[0022]FIG. 6 is a flowchart of the processings executed by a LU changecontroller of the present invention.

[0023]FIG. 7 is a flowchart of the processings executed in an accessfrequency counter of the present invention.

[0024]FIG. 8 is an example of the format of the LU change table of acomputer that accesses the SAN according to the present invention.

[0025]FIG. 9 is an example of the format of the access frequencymanagement table of a management computer according to the presentinvention.

[0026]FIG. 10 is an example of the screen for displaying an accessfrequency totaled by the management computer according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] Hereunder, an embodiment of the present invention will bedescribed with reference to the accompanying drawings.

[0028]FIG. 1 shows an overall block diagram of a disk storage accessmanagement system of the present invention.

[0029] This system is composed of a management computer (100); a SANmanagement computer (110) for managing a SAN (140); and a SAN referencecomputer 1 (120) and a SAN reference computer 2 (130) for accessing SANdisk storages respectively. The management computer (100) is connectedto the SAN management computer (110), the SAN reference computer 1(120), and the SAN reference computer 2 (130) via a LAN (170)respectively. The system of the present invention controls accesses toeach SAN (140) disk storage by enabling the management computer (100) tomanage the frequency of accesses to each disk storage from each of theSAN reference computer 1 (120) and the SAN reference computer 2 (130).

[0030] The management computer (100) is provided with a resourcemonitoring/management unit (101) for managing the disk storage accessfrequency in each of the SAN reference computer 1 (120) and the SANreference computer 2 (130), as well as an access frequency managementtable (103) used for managing the disk storage access frequency and aSAN controller (102) for issuing requests to the SAN.

[0031] The SAN management computer (110) is provided with a DKUcontroller for instructing copying or deleting a DKU volume according tothe request from the SAN controller.

[0032] Each of the SAN reference computer 1 (120) and the SAN referencecomputer 2 (130) is provided with an application program (122)/(132)used to access disk storages of the SAN (140); a LU (Logical Unit)change controller (123/133) used to control the disk storage access pathof the application program (122/132); an LU change table (125/135) usedto manage the disk storage access path; an access frequency counter(124/134) used to count the frequency of accesses to each disk storage;and a resource monitoring unit (121/131) used to answer the disk storageaccess frequency to the resource monitoring/management unit (101).

[0033] A plurality of disk storage units are connected to the SAN (140)and each of those disk storage units is provided with a DKC (diskstorage controller)(151/161); a disk storage volume controller (152/162)used to control the disk volume (logical volume) and a disk storage unit(DKU)(153/163), which is an actual disk storage.

[0034]FIG. 2 shows a flowchart of the processings executed by theresource monitoring/management unit (101).

[0035] The resource monitoring/management unit (101) inquiries theresource monitoring unit (121/131) periodically about an accessfrequency for each disk storage unit (step 200) and totals the accessfrequency data of the disk storage unit obtained from the resourcemonitoring unit (121/131) (step 202) in the access frequency managementtable (103).

[0036] When the access frequency of a disk storage is over apredetermined high threshold value (step 204), the resourcemonitoring/management unit (101) requests the SAN controller (102) tocopy the disk volume into one or more other disk storage units (step206).

[0037] When the disk storage unit access frequency is under apredetermined low threshold value (step 208) and the target data isalready copied in one or more disk storage units (step 210), theresource monitoring/management unit (101) requests the SAN controller(102) to delete the disk volume from one or more of the disk storageunits (step 214).

[0038] In other cases, the resource monitoring/management unit (101)executes no operation (step 212).

[0039]FIG. 3 shows a flowchart of the processings executed by the SANcontroller (102).

[0040] The SAN controller (102), when receiving a request from theresource monitoring/management unit (101)(step 300), executes therequested processing (step 302).

[0041] When the request is a volume copy one, the SAN controller (102)requests the DKU controller (111) to copy the disk volume into one ormore other disk storage units (step 304).

[0042] Receiving a report on completion of the volume copying from theDKU controller (111), the SAN controller (102) requests the LU changecontroller (135) of the SAN reference computer 2 (13) that has accessedthe disk unit most frequently to change access paths so as to access thetarget disk storage Y from the copy source disk storage X (step 308).

[0043] For example, when there are three or more SAN referencecomputers, the access path of the SAN reference computer that hasaccessed the subject disk unit most frequently is changed to another soas to average the access frequencies of the paths.

[0044] When the request is a volume deletion one, the SAN controller(102) requests the LU change controller (135) of the SAN referencecomputer 2 (130) to change access paths so as to access the disk storageX (copy source) from the target disk storage Y (step 310).

[0045] After that, the SAN controller (102) requests the DKU controller(111) to delete the target disk volume (step 312).

[0046] Because the main object of the present invention is to refer tocontents in Web servers, etc., copied data in disk storages are notupdated directly from any SAN reference computer.

[0047] When data in the disk storage X (copy source) is updated, thedata is copied from the disk storage X (copy source) into the targetdisk storage Y again according to a command issued to the subject SANmanagement computer. When there are a plurality of target disk storages,data in the copy source disk storage X is copied again into those diskstorages.

[0048]FIG. 4 shows a flowchart of the processings executed by the DKUcontroller (111).

[0049] The DKU controller (111), when receiving a request from the SANcontroller (102) (step 400), executes the requested processing (step402).

[0050] When the request is a volume copy one, the DKU controller (111)issues a volume copy request to the DKC (151) (step 404).

[0051] When receiving a report on completion of the volume copying fromthe DKC (151)(step 406), the DKU controller (111) reports the completionof the volume copying to the SAN controller (102) that is the requestsource (step 408).

[0052] When the request is a volume deletion one, the DKC controller(111) issues a disk storage unit volume deletion request to the DKC(151) (step 410).

[0053]FIG. 5 shows a flowchart of the processings executed by theresource monitoring unit (121/131).

[0054] The resource monitoring unit (121/131), when receiving an inquiryfrom the resource monitoring/management unit (101) (step 500), obtainsan access frequency of the target disk storage from the access frequencycounter (124/134) (step 502).

[0055] The resource monitoring unit (121/131) then sends the obtaineddata to the resource monitoring/management unit (101) (step 504).

[0056]FIG. 6 shows a flowchart of the processings executed by the LUchange controller (123/133).

[0057] The LU change controller (123/133), when receiving a request(step 600), executes the requested processing (step 602).

[0058] When the request is an LU change table updating one, the LUchange controller (123/133) updates the LU change table (125/135) andchanges access paths so as to access another disk storage (step 604).

[0059] When the request is a disk storage access one from an applicationprogram, the LU change controller (123/133) searches in the LU changetable (125/135) so as to decide a new disk storage access path (step606).

[0060] The LU change controller (123/135) then sends an access requestto the DKC corresponding to the decided access path (step 608).

[0061]FIG. 7 shows a flowchart of the processings executed by the accessfrequency counter.

[0062] The access frequency counter (124/134), when receiving an accessfrequency obtaining request (step 700), calculates an access frequencyfrom each disk storage access count or the accessed data amount countdata of each disk storage (step 702) and sends the calculated accessfrequency to the request source (step 704).

[0063]FIG. 8 shows a format of the LU change table (125/135).

[0064] An LU change table is a table on correspondence between each LUnumber accessed by an application program and a DKU number, whichdenotes a target disk storage.

[0065] In the initial state, the LU change table of the SAN referencecomputer 1 defines X(801) as the DKU number corresponding to the LUnumber 1 and Y(802) as the DKU number corresponding to the LU number 2.

[0066] The LU change table of the SAN reference computer 2 defines X asthe DKU number corresponding to the LU number 1, but the DKU number ischanged from X to Y when an access frequency at volume copying exceeds apredetermined high threshold value (step 811).

[0067] The DKU number corresponding to the LU number 2 is Z.

[0068]FIG. 9 shows a format of the access frequency management table(103).

[0069] The access frequency management table is used to manage accessfrequency data collected from SAN disk storages of each computer.

[0070] For example, the access frequency management table manages theaccess frequency of the disk storage X, which is obtained from the SANreference computer 1 (step 901), as well as the access frequency ofanother disk storage, which is obtained from the SAN reference computer2 (step 902).

[0071]FIG. 10 shows an example of access frequencies displayed on ascreen.

[0072] The access frequency data managed as shown in FIG. 9 anddisplayed in FIG. 10 is totaled for each disk storage.

[0073] The access frequency of each disk storage is displayed withrespect to each data collecting time.

[0074] The screen in FIG. 10 also shows the minimum value, the maximumvalue, and the average value of each collected access frequency data.

[0075] While the embodiment of the present invention has been described,the DKU controller in the SAN management computer shown in FIG. 1 mayalso be moved into a management computer as a component thereof.

[0076] Furthermore, instead of the management computer and the SANmanagement computer shown in FIG. 1, the system may be provided withjust one mean that includes the SAN controller, the resourcemonitoring/management unit, and the access frequency management tablethat are all included in the management computer, as well as the DKUcontroller that is included in the SAN management computer.

[0077] The above means may be provided only in one of a plurality of theSAN reference computers.

[0078] According to the present invention, therefore, it is possible todisperse the load of each disk storage accessed from a plurality ofcomputers so as to cope with changes of the load flexibly.

What is claimed is:
 1. A disk storage accessing system for enabling aplurality of computers to share and access a disk storage, said systemcomprising: a plurality of computers that refer to said disk storage,each of said computers including: counting means for counting afrequency of accesses to said disk storage; means for receiving anaccess path change command so as to change access paths so as to accessa disk storage from a computer according to said command; wherein saidsystem includes instructing means for collecting and totaling afrequency of accesses to a disk storage, counted by each of saidcomputers, as well as instructing said disk storage to copy its contentsinto one or more other disk storages when said access frequency ishigher than a predetermined value, and instructing a computer thataccesses said copy source disk storage after receiving a report of copycompletion, to change access paths so as to access a target disk storagefrom said copy source disk storage.
 2. The disk storage accessing systemaccording to claim wherein said system, when instructing a computer thataccesses said copy source disk storage to change access paths so as toaccess a target disk storage from said copy source disk storage, issuessaid instruction to a computer that has accessed said copy source diskstorage most frequently.
 3. The disk storage accessing system accordingto claim wherein said instructing means of said system is provided inany one of a plurality of said computers.
 4. The disk storage accessingsystem according to claim wherein said system, when data in said copysource disk storage is updated, enables said data in said copy sourcedisk storage to be copied again into one or more of said disk storages.5. A disk storage accessing system for enabling a plurality of computersto share and access a disk storage, said system comprising: a pluralityof computers for referring to said disk storage respectively and amanagement computer; wherein each of a plurality of said computers thatrefer to said disk storage is provided with counting means for countinga frequency of accesses to said disk storage; and said managementcomputer is provided with means for collecting and totaling a frequencyof accesses to said disk storage, counted by each of a plurality of saidcomputers, as well as instructing said disk storage to copy its datainto one or more other disk storages when said totaled access frequencyis higher than a predetermined value and instructing a computer thataccesses said copy source disk storage after receiving a report oncompletion of said copying, to change access paths so as to access atarget disk storage from said copy source disk storage; and each ofcomputers that refer to said disk storage is provided with means forreceiving an access path change command from said management computer tochange access paths and access a target disk storage according to saidcommand.
 6. The disk storage accessing system according to claim 5;wherein said system, when instructing a computer that accesses said copysource disk storage to change access paths so as to access a target diskstorage from said copy source disk storage, issues said instruction to acomputer that has accessed said copy source disk storage mostfrequently.
 7. The disk storage accessing system according to claim 5;wherein said system, when data in said copy source disk storage isupdated, enables said updated data to be copied from said copy sourcedisk storage into one or more other disk storages again.
 8. A diskstorage accessing system for enabling a plurality of computers to shareand access a disk storage respectively, said system comprising: aplurality of computers for referring to said disk storage respectively;a first management computer; and a second management computer; whereineach of a plurality of said computers that refer to said disk storage isprovided with counting means for counting a frequency of accesses tosaid disk; said first management computer is provided with means forcollecting and totaling a frequency of accesses to said disk storage,counted by each of a plurality of said computers and sending a copycommand to said second management computer so as to copy said data fromsaid disk storage into one or more other disk storages when said totaledaccess frequency is higher than a predetermined value; said secondmanagement computer is provided with means that, when receiving saidcopy command, instructs said disk storage to copy its data into one ormore other disk storages; and said first management computer is furtherprovided with means that, when receiving a report on completion of saidcopying from said second management computer, instructs a computer thataccesses said copy source disk storage to change access paths so as toaccess a target disk storage from said copy source disk storage; andeach of a plurality of said computers that refer to said disk storage isprovided with means for receiving an access path change command fromsaid first management computer so as to change access paths and access atarget disk storage from a computer according to said command.
 9. Thedisk storage accessing system according to claim 8; wherein said system,when instructing a computer that accesses said copy source disk storageto change access paths so as to access a target disk storage from saidcopy source disk storage, sends said command to a computer that hasaccessed said copy source disk storage most frequently.
 10. The diskstorage accessing system according to claim 8; wherein said system, whendata in said copy source disk storage is updated, enables said data tobe copied from said copy source disk storage into one or more other diskstorages again.